1. Field of the Invention
The invention relates to a method for sealing off a separating gap, formed between a rotor and a stator, in a non-contacting manner, from the throughflow of a working fluid admitted to the separating gap, to an arrangement for carrying out the method.
2. Discussion of Background
In the construction of fluid-flow machines, labyrinths, i.e. non-contacting motion seals, are often used to seal off components rotating at high speed. A multiplicity of the most diverse labyrinth seals are known, but their operating principle is always based on minimizing the fluid mass flow through the labyrinth. To this end, they generally have a plurality of sealing elements, which are of similar construction and are arranged one after the other in the direction of flow of the working fluid, for the separating gap which is formed between the rotor and the stator and is to be sealed off. Each sealing element consists of at least one choke point and a vortex chamber adjoining downstream, the choke point and the vortex chamber being more or less greatly pronounced in the many different labyrinth seals. By the arrangement of sealing elements in a row, the flow resistance can be increased as desired and thus the fluid quantity passing through the seal can be kept small.
The textbook "Beruhrungsfreie Dichtungen" by K. Trutnovsky, VDI-Verlag GmbH, Dusseldorf 1981, 4th edition, ISBN3-18-400490-2, page 244/245, FIGS. 4-58 and 4-59 discloses labyrinth seals in which the surface opposite the choke points is given a particular fluidic design. Thus, these surfaces have conical widened portions with adjoining hollow bulbous surfaces or curved niches. It is thus possible to both extend the flow path up to the next choke point and prevent the shooting of flow filaments straight through the gap, as a result of which the fluid mass flow passing through the seal can ultimately be further reduced.
In the known labyrinth seals, considerable friction power occurs as a result of the forming flow boundary layers in the separating gap, through which fluid flows, between the rotating and the stationary components. This leads to heating of the working fluid in the separating gap and thus likewise to heating of the components surrounding the separating gap. In this way, the material temperatures may increase to a relatively high degree, which results in a reduced service life of the components affected. In addition, the deflection and swirling of the working fluid, flowing through the separating gap, at the choke points lead to continuous intermixing of the working fluid, combined with a high impulse and heat exchange. Downstream of the choke point, the working fluid must in each case be accelerated again in the circumferential direction at the rotating component, as a result of which the friction power and thus the development of heat in this region continue to increase.